To measure pressure in fluid systems, differential pressure sensors are often used in combination with some sort of valve assembly, which has a primary purpose of protecting the differential pressure sensor against extreme continuous pressures or pressure shocks that higher than the sensor can handle. Such assemblies often also have functions for flushing the assembly to get rid of enclosed air in cavities and have functions to calibrate the differential pressure sensor, a so called zero point calibration. The purpose of the calibration procedure is to ensure that before measuring begins, both measuring sides of the pressure sensor have the same pressure.
There are several examples of devices addressing the problem of how to protect a differential pressure sensor against prohibited differential pressure levels. Examples of such solutions are DE 19503488, which describes a device with two safety valves (4, 5) that protects the differential pressure sensor against prohibited differential pressure levels, and also GB 2091883 A, which also describes a device with safety valves (46, 48) for protecting against prohibited differential pressure levels.
Moreover there is a solutions, in GB 2 410 332 A, which includes the functions of zero point calibration and flushing a valve assembly, where two safety valves (36, 38) are utilized to protect the differential pressure sensor (26) against prohibited differential pressure levels. The two safety valves (36, 38) in this device are designed as non return valves, which each protect a connection side at the differential pressure sensor. Depending on which side of the connection is connected to the highest pressure, the respective safety valve protects one side/direction each.
The problem with earlier solutions, for instance the solution described in GB 2 410 332 A above, is that at least two safety valves are required, and with them are arranged ducts, to protect the complete valve assembly against extreme differential pressures, which consequently makes the manufacturing the device more expensive and more difficult.